package demo1;

public class Solution {
    public int tribonacci(int n) {
        int[] dp = new int[n+1];

        if(n == 0) return 0;
        if(n == 1 || n == 2) return 1;

        dp[0] = 0;
        dp[1] = dp[2] = 1;
        for (int i = 3; i < n; i++) {
            dp[i] = dp[i-1] + dp[i-2] + dp[i-3];
        }
        return dp[n];
    }

    public int answer2(int n){

        if(n == 0) return 0;
        if(n == 1 || n == 2) return 1;

        int a = 0, b = 1, c = 1;
        for (int i = 3; i <= n; i++) {
            int d = a + b + c;
            a = b;
            b = c;
            c = d;
        }
        return n;
    }

    public int fun1(int n){
        int[] dp = new int[n];

        if(n == 0) return 0;
        if(n == 1 || n == 2) return 1;

        dp[0] = 0;
        dp[1] = dp[2] = 1;
        for (int i = 3; i <= n; i++) {
            dp[i] = dp[i-1] + dp[i-2] + dp[i-3];
        }
        return dp[n];
    }
}
